KR100557542B1 - Optical pick-up apparatus having a optical detective area to compensate tracking error offset - Google Patents

Abstract

The optical pickup apparatus according to the present invention detects a tracking error of a DVD-RAM disc by adjusting the angle of the side beam to use a conventional differential push-pull method (DPP) based on a DVD-RAM disc, and has a different track pitch. In the case of DVD-ROM / ± R / ± RW discs, instead of the differential push-pull method, the optical lens is focused on a predetermined light detection area in which the tracking error signal is not formed in the light detection pattern. Compensate for tracking error offsets that occur.

Accordingly, the present invention accurately detects tracking / focus error signals for optical discs having different track pitches by compensating tracking offsets due to the deviation of the optical axis of the objective lens by using the light distribution of the photodetection area where the tracking error signal is not formed. It provides the effect that you can.

Optical pickup, tracking error offset, center beam, side beam, photodetector, photodetector, differential astigmatism (DAD), differential push-pull (DPP) method, modified push-pull (MPP) method, astigmatism method.

Description

Optical pick-up apparatus having a optical detective area to compensate tracking error offset}

1 is a top view showing the structure of a quadrant photodetector used in an optical pickup device;

2 is a view for explaining the principle of the push-pull method of performing tracking servo tracking of the optical pickup device.

3 is a diagram illustrating light intensity distribution of light spots focused on a photodetector of the optical pickup apparatus.

4 is a view showing a light intensity distribution of light spots formed by the emission beam of the laser diode according to the optical pickup device.

Fig. 5 is a diagram showing a light spot shape formed by diffraction beams incident from an optical disc (DVD ± R / RW).

FIG. 6 is a diagram showing an optical spot shape formed by diffraction beams incident from an optical disc (DVD-RAM). FIG.

7 is a diagram illustrating a configuration of an optical pickup apparatus for performing servo tracking of an optical disc using a conventional differential push-pull (DPP) scheme.

Fig. 8 is a diagram showing the configuration of a light detecting element formed in a conventional optical pickup apparatus.

9 is a diagram illustrating a configuration of an optical pickup apparatus in which a photodetection area for tracking error offset compensation is formed according to the present invention.

10 is a diagram showing focusing positions of a center beam and side beams of a diffraction beam focused on optical disks having different track pitches;

Fig. 11 is a diagram showing the configuration of light detecting means in which a light detecting area for tracking error offset compensation according to a first embodiment of the present invention is formed;

Fig. 12 is a diagram showing the configuration of light detecting means in which a light detecting region for tracking error offset compensation according to a second embodiment of the present invention is formed.

Fig. 13 is a diagram showing the configuration of light detecting means in which a light detecting area for tracking error offset compensation according to a third embodiment of the present invention is formed;

Explanation of symbols on the main parts of the drawings

100: light emitting means 200: optical means

210: diffraction plate 220: beam splitter

230: collimator lens 240: wave plate

250: objective lens 300: light detection means

310, 310 ', 310' ': first photodetector

 320, 320 ', 320' ': second photodetector

330, 330 ', 330' ': third light detector

400: optical disc

The present invention relates to an optical pickup apparatus having a photodetection area for tracking error offset compensation.

More specifically, by using the light distribution of the photodetection area in which the tracking error signal is not formed among the photodetectors formed in the photodetection means, the tracking offset according to the deviation of the optical axis of the objective lens is compensated for an optical disc having a different track pitch. An optical pickup apparatus for performing focus / tracking servo tracking.

Recently, due to the large capacity of the information data, the information data is stored by changing a predetermined optical method, more specifically, the transmittance, reflectance, phase, polarization, etc. of the light where the information data is stored, and change the information data. Background Art Optical discs for reading information by reading light are being developed.

In other words, the optical disk is a disk-shaped disk, the information is stored, and irradiates the focused laser light to read the information by reading the reflectance or the phase or polarization change of the light at the time of reflection, the wavelength of light on the disk It is a storage medium that generates minute grooves of a size and generates digital signals of '1' and '0' depending on the presence or absence of grooves.

Currently, in the optical disc market, optical discs with different track pitches, more specifically DVD-RAM discs (track pitch 1.23 μm, 1.48 μm) and DVD-ROM / ± R / ± RW (track pitch 0.74 μm), are compatible. The DVD multimedia system can be spread rapidly, and in conjunction with this, optical pickup devices are required to have compatibility for storing predetermined information data on optical disks having different track pitches or reading information data stored on optical disks. will be.

Here, the optical pickup apparatus forms an aberration-free laser on the optical disk in order to record / reproduce information data recorded on the optical disk, and reflects the amount of light reflected by the diffracted interference of the information pit of the optical disk. After focusing, it converts it into an electrical signal.

That is, the optical pickup apparatus stores a predetermined information data on an optical disk of a DVD system, or uses a push-full method or a differential push-pull (DPP) using one beam to read the information data stored on the optical disk. The tracking / servo following of the optical disc was performed using the method.

As shown in FIG. 1, the push-pull method among the tracking / servo tracking methods of the optical disc, as described above, provides a difference in the amount of light detected by a predetermined shape, more specifically, a quadrature photo detector (PD). Used as a tracking error signal, where the tracking error signal is

Tracking error signal TES = (a + c)-(b + d).

That is, when the light spot formed by the central beam focused on the optical disk through the objective lens and the light spot formed by both side beams are accurately followed along the signal track of the optical disk as shown in FIG. As shown in FIG. 4, the tracking error signal TES for the optical disc is detected by the optical distribution of each divided region.

At this time, when the light beam focused from the objective lens OL follows the center of the signal track, the light distribution difference of the photodetector PD appears uniformly and is calculated as an electrical signal by (a + c)-(b + d). The resulting tracking error signal has a magnitude of zero.

However, when the light beam from the objective lens OL is focused to the right in the signal track, the light distribution difference of the photodetector PD is irradiated with more light on the right side than on the left side so that (a + c)-(b + d The tracking error signal of the result calculated by the electrical signal of) appears as a signal having a magnitude of +.

In addition, when the light beam from the objective lens OL is condensed to the left in the signal track, the light distribution difference of the photodetector PD is irradiated with more light on the left side than on the right side so that (a + c)-(b + d The tracking error signal of the result calculated by the electrical signal of) appears as a signal having a magnitude of-.

As described above, when the tracking error signal is detected by the photodetector PD, the optical pickup device drives the actuator in association with the detected tracking error signal, whereby the light beam from the objective lens OL is the center of the signal track. Tracking servo on the optical disc was performed by following the step.

In tracking servo tracking for such an optical disc, the optical spot focused on the track pitch of the optical disc is required to have a small light intensity change with respect to the tracking shift caused by the left and right movement of the objective lens.

However, the optical spot focused on the track pitch of the optical disc has a high light intensity distribution in the center spot region and a low light intensity distribution in the peripheral spot region, as shown in FIG. When the objective lens moves left and right, a tracking offset error occurs, which makes it difficult to accurately follow the tracking servo.

In addition, even when accurate tracking servo tracking is performed on the optical disk, when the diffracted beam reflected from the optical disk is filtered by the diameter of the objective lens, the balance between the left and right light distributions of the optical spot is not maintained, whereby Although tracking servo tracking is being performed, there has been a problem that a tracking offset error is generated in which a tracking error signal for an optical disc is output.

That is, in the case of a DVD-ROM / ± R / ± RW optical disc having a track pitch of 0.74 μm, as shown in FIG. 5, the diffraction beam having a diffraction angle larger than the incident angle that the objective lens can accommodate is an objective lens. Only diffraction beams filtered by and having a 0th order and ± 1st order diffraction coefficient that are not filtered by the objective lens are incident on the light detecting means to form a light spot having a base shape.

In addition, in the case of a DVD-RAM optical disc having a track pitch of 1.23 µm / 1.48 µm, as shown in FIG. 6, a track pitch relatively larger than that of the DVD-ROM / ± R / ± RW optical disc is shown. This results in a small diffraction angle, so that the incident diffraction beam is incident on the light detecting means without being filtered by the objective lens.

At this time, when the objective lens is shifted in the left and right directions, the center beam having the lightest intensity is the highest among the light spots formed by the diffraction beam reflected after the tracking of the optical disk. Moving in the right direction, so that the tracking error offset signal for the optical disc is detected.

That is, although the tracking servo for the optical disk has been successfully performed, the center beam of the optical spot moves in conjunction with the left and right shifts of the objective lens, thereby successfully tracking the servo due to the difference in the balance of the light intensity distribution. By generating a tracking error offset signal that it has not been performed, it becomes impossible to perform accurate tracking servo estimation for the optical disc.

In addition, as another method of performing tracking / servo following of an optical disc, Korean Patent Laid-Open No. 2001-0098602 discloses a technical idea of detecting a tracking error signal using a DPP (Differential Push-Pull) method.

That is, as described in Korean Patent Laid-Open No. 2001-0098602, as shown in FIG. 7, the laser light source 2 generating the beam light B and the beam light B emitted from the laser light source 2 are diffracted. A beam diffraction means (3), a beam splitter (4) for reflecting the beam light (B) in a predetermined direction, or a beam collimator (B) for condensing the beam light (B) on the signal surface of the collimator lens (5) and the optical disk (6) forming parallel light beam An optical pickup device (1) having an objective lens (7) and a photo detector (8) for receiving a feedback light from the optical disc (6) is disclosed.

Here, as shown in FIG. 8, the photo detector 8 constituting the optical pickup device 1 includes a main photo detector 8a and two side photo detectors 8b and 8b. The main photo detector 8a is divided into four vertically and horizontally to receive the main spot MS, and the side photo detectors 8b and 8b are respectively divided into two left and right to receive side spots SS and SS.

At this time, the output signal of each division element is represented by A, B, C, D, E, F, G, H as in the conventional technique, and outputs from these photodetectors 8a, 8b, 8b. Generate a tracking error signal from the computational output between the signals.

That is, the main photo detector has four vertical and horizontal light receiving sections, and the side photo detectors have two left and right photo receiving sections, and each photo detector generates a separate push-pull signal, and tracking error is calculated from the operation output of these push-pull signals. While generating a signal, the DC offset amount generated in the push-pull signal in each photo detector is canceled for each push-pull signal, so that the DC offset amount between the SPP1 signal and the SPP2 signal is different regardless of the calculation formula. It is possible to prevent the offset amount from occurring in the DPP signal, to enable high-precision tracking servo, and to achieve higher recording density.

However, the DPP (Differential Push-Pull) method as described above requires accuracy in positioning the auxiliary beam at the track boundary, so that it is difficult to simultaneously apply to optical discs having different track pitches and to use discs having different track pitches. There is a disadvantage in that the tracking error signal is significantly reduced when reading, thereby preventing servo.

That is, when the position of the side beam is adjusted to any one type of disk, as shown in Fig. 3, since the center beam and side beam of the diffraction beam are focused at the center of the track pitch, the conventional split astigmatism method and differential The push-pull method was used to detect the tracking / focus error signal of the optical disc.

However, when a disc having a different track pitch is read out, as shown in FIG. 3, although a focusing error signal can be detected using astigmatism, the side beam is not focused at the center of the track pitch. There was a problem in that the tracking error signal of the optical disc could not be detected by using the differential push-pull method.

In order to solve the above-described problems, the present invention provides a DVD-ROM that detects a tracking error of a RAM disk by adjusting the angle of the subbeam to use a conventional DPP method based on a DVD-RAM disk, and has a different track pitch. In the case of / ± R / ± RW discs, instead of the DPP method, an optical intensity distribution focused on a predetermined light detection area in which the tracking error signal is not formed in the light detection unit is used to compensate for the tracking error offset caused by the deviation of the optical axis of the objective lens. The present invention provides an optical pickup apparatus that detects a tracking error by performing a compensation on the same.

According to an aspect of the present invention, there is provided an optical pickup apparatus comprising: light emitting means for emitting a single beam focused on an optical disc having different track pitches to the outside; Optical means for concentrating a light spot of a diffraction beam having a predetermined diffraction coefficient formed by performing diffraction on the single beam to the track pitch, and transmitting the diffracted beam reflected by the track pitch to the outside; And a first light detector configured to focus a center beam having a zeroth order diffraction coefficient among the diffracted beams incident from the optical means, and second and third light detectors focused on a side beam having a first order diffraction coefficient, respectively. The photodetector is divided into a predetermined number of photodetection regions, and at least one photodetector has a photodetection region in which a tracking error signal used for compensating for a tracking offset caused by the deviation of the optical axis of the objective lens is not formed. It is characterized by including a light detecting means.

Hereinafter, an optical pickup apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

First, a configuration of an optical pickup apparatus in which a photodetection area for tracking error offset compensation according to the present invention is formed will be described with reference to FIG. 9.

The optical pickup apparatus having the optical detection area for tracking error offset compensation according to the present invention has a tracking / focus error by using the reflection of the optical disk and the light intensity distribution of the diffraction beam when the emission beam of the objective lens coincides with the track center of the optical disk. Detecting a signal and tracking / focus error signal by performing tracking error offset compensation using the light intensity distribution of the light detection area where the tracking error signal is not imaged or less affected when it does not match the track center of the optical disc. 9, the light emitting means 100, the optical means 200, and the light detecting means 300 are configured to be included.

Here, the light emitting unit 100 records and reproduces audio / video information data on the optical disc 400 having a track pitch having a predetermined shape, or focus / tracking for accurately reading the information data recorded at the track pitch. It is a laser diode which emits laser light for detecting a signal, for example, emits laser light having a wavelength of 780 nm or 650 nm.

Optical means 200 serves to focus the laser light emitted from the light emitting means 100 on the track pitch formed on the optical disk 400, as shown in Figure 9, the diffraction plate 210 And a beam splitter 220, a collimator lens 230, a wave plate 240, and an objective lens 250.

Here, the diffraction plate 210 performs a diffraction on the laser light emitted from the light emitting means 100 to perform a linear waveform having a predetermined diffraction coefficient, more specifically, a diffraction coefficient of 0th order, + 1, -1st order. After forming the laser light, and serves to transfer it to the beam splitter 220, more specifically grating.

The beam splitter 220 serves to branch the laser light in the form of linearly polarized light having a predetermined diffraction coefficient incident from the diffraction plate 210 in the direction in which the optical disc 400 is located.

In addition, the beam splitter 220 receives the laser light reflected from the optical disc 400, and then the light detecting means 300 which describes the laser light for tracking / servo estimation of the optical disc 400 is located. It also serves to branch in the direction.

The collimator lens 230 converts the linearly flat laser light having a predetermined diffraction coefficient branched by the beam splitter 220 into parallel light and enters the wave plate 240.

The wavelength plate 240 forms a circularly polarized laser light from a linearly polarized laser light having a predetermined diffraction coefficient incident in parallel from the collimator lens 230, and then enters the objective lens 250. do.

The objective lens 250 is an optical disk 500 for storing predetermined image and audio data information for the laser beam incident from the wave plate 240, and more specifically, a DVD-RAM having a track pitch of 1.23 μm / 1.48 μm. It serves to condense the track pitch on a disc or a DVD-ROM / ± R / ± RW disc with a track pitch of 0.74 μm.

The photodetector 300 may include a first photodetector configured to focus a center beam having a zeroth order diffraction coefficient among diffraction beams incident through the optical means 200, a second beam focused on a side beam having a ± 1st order diffraction coefficient, and And a third optical detector, wherein the photodetector is divided into a predetermined number of photodetection regions, and at least one photodetector is formed with a tracking error signal used to compensate for tracking offsets caused by deviation of the optical axis of the objective lens. The photodetection area | region which is not made is formed.

At this time, when the center beam and side beam of the diffracted beam incident through the optical means are focused on the track center of the DVD-RAM optical disc 400 having a track pitch of 1.23 mu m as shown in FIG. 11 to 13, the first photodetector 310, 310 ′, 310 ″, the second photodetector 320, 320 ′, 320 ″ and the third photodetector Detecting the focus error signal of the optical disc 400 using differential astigmatic detection (DAD) by the light intensity distribution of the center beam and the side beam focused on the (330), (330 ", 330"), respectively. do.

In addition, the light detecting means 300 may include a first light detector 310, 310 ′, 310 ″, a second light detector 320, 320 ′, 320 ′, and a third light detector 330 ( The tracking error signal of the optical disk 400 is detected by using a differential push-pull (DPP) method by the light intensity distribution of the center beam and the side beam focused on the 330 "and 330", respectively.

The photodetecting means 300 includes a DVD ± R / RW optical disc 400 in which a diffraction beam having a 0th order and ± 1st order diffraction coefficient through the optical means 200 has a track pitch of 0.74 mu m as shown in FIG. ), A focus error signal of the optical disc is detected by using an astigmatism method based on the light intensity distribution of the central beam focused on the first light detectors 310, 310 ′, 310 ″.

In this case, the DVD ± R / RW optical disc 400 has a narrower track pitch compared to a DVD-RAM optical disc, so that the side beam is not located in the middle region of the land portion, so that the differential push-pull method (DPP) is different. When the tracking error signal is not detected by using the above-described method, the photodetector 300 may include the first photodetector 310, 310 ′, 310 ″, and the second photodetector 320, 320 ′, 320. The modified push-pull method (MPP :), which uses the light intensity distribution of the photodetection area in which the tracking error signal is not formed in the ") and the third photodetectors 330, 330 'and 330 ", for tracking error offset compensation. The tracking error signal of the optical disc 400 is detected by Modified Push-Pull.

Here, the detection of the focus / tracking error signal of the optical disc is based on a state where the center beam and the side beam of the diffraction beam coincide with the track center of the DVD-RAM optical disc and do not coincide with the track center of the DVD ± R / RW optical disc 400. Although described as, it should be noted that the present invention is not limited thereto and vice versa.

Hereinafter, referring to FIGS. 11 to 13, a process of detecting a tracking / focus error signal of an optical disc having a different track pitch using light distribution of a diffraction beam focused on a light detection pattern having a predetermined shape formed on the light detection means will be described in more detail. The explanation is as follows.

(First embodiment)

The light detecting means 300 is a place where the light spot 500 formed by the center beam and the side beam of the diffraction beam having a predetermined diffraction coefficient incident from the optical means 200 is focused, as shown in FIG. 11. Similarly, the first photodetector 310, the second photodetector 320, and the third photodetector 330 are configured.

Here, the first photodetector 310 includes (A1) (B1), (A2) (B2), (D2) (C2) and (D1) (in which a central beam having a zero-order diffraction coefficient is focused among the diffracted beams. C1) It is divided into 8 parts by the light detection area.

Here, the (A2) (B2) and (D2) (C2) photodetection regions formed in the central portion of the first photodetector 310 are photodetection regions in which a tracking error signal is not formed, and the light of the photodetection region. The intensity distribution is used to compensate for the tracking error offset caused by the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the diffraction beam is not focused at the track center.

In addition, the second photodetector 320 is formed in the upper direction of the first photodetector 310 and (E1) (E2) and (F1) (F2) in which side beams having a + 1st order diffraction coefficient are focused. It is divided into four areas.

In addition, the third photodetector 330 is formed in the lower direction of the first photodetector 310 and (I1) (I2) and (J1) (J2) in which side beams having a -first-order diffraction coefficient are focused. It is divided into four areas.

At this time, as shown in FIG. 10 through the optical means 200, the center beam and the side beam of the diffraction beam coincident with the track center of the DVD-RAM optical disc 400 having a track pitch of 1.23 mu m are first and second. And when focused on the third light detectors 310, 320, and 330, the light detector 300 is divided into the light detectors 310 and 320, which are divided into predetermined shapes as shown in FIG. The focus error signal of the DVD-RAM optical disc 400 is detected by a differential astigmatic detection (DAD) method using light intensity distributions of the center beam and the side beam of the diffracted beam focused at 330.

(Equation 1)

Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2)

                        + β ((E1 + F2 + I1 + J2)-(F1 + E2 + J1 + I2)]

Here, A1, A2, B1, B2, C1, C2, D1, D2, E1, E2, F1, F2, I1, I2, and J1, J2 are voltages corresponding to the amount of light focused in each region, and β is It means gain.

In addition, the light detecting means 300 is a differential push-pull method (DAD) for calculating the light intensity distributions of the center beam and the side beam of the diffracted beam focused on the light detectors 310, 320, and 330. ) Detects a tracking error signal of the DVD-RAM optical disc 400.

(Equation 2)

Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)

                        β ((E1 + E2 + I1 + I2)-(F1 + F2 + J1 + J2)]

At this time, the optical disc 400 has a narrower track pitch, more specifically, a track pitch of 0.74 µm, as compared to a DVD-RAM optical disk as shown in FIG. 10, so that the side beam does not coincide with the track center. In the case of an RW optical disc, the photodetecting means 300 is subjected to astigmatism using the light intensity distribution of the first photodetector 310 in which a central beam having a zero-order diffraction coefficient is focused, as shown in FIG. By this, the focus error signal of the DVD R / RW optical disc 400 is detected.

(Equation 3)

Focus error signal (FES) = (A1 + C1)-(B1 + D1)

or,

Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2)

Further, the photodetecting means 300 is an intermediate region in which the tracking error signal is not formed in the zeroth order diffraction beam focused on the first photodetection pattern 311, more specifically, (A2), (B2), and (D2). DVD ± R / by the Modified Push-Pull (MPP) method, which uses the light intensity distribution in the (C2) and (C2) regions to compensate for the tracking offset caused by the deviation of the optical axis of the objective lens 250. The tracking error signal of the RW optical disc 400 is detected.

(Equation 4)

      Tracking error signal (TES) = (A1 + B1)-(C1 + D1)-β ((A2 + B2)-(C2 + D2)]

Here, the light detecting means 300 generates the light intensity distribution in the (A2), (B2), (D2) and (C2) regions, which are intermediate regions in which the tracking error signal is not formed, as the optical axis of the objective lens 250 is out of the optical axis. The tracking error signal of the DVD ± R / RW optical disc 400 may also be detected by another modified push-pull (MPP) method used to compensate for the tracking offset.

(Equation 5)

Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)

                        β ((A2 + B2)-(C2 + D2))

(Second embodiment)

The light detecting means 300 is a place where a light spot 500 formed by a diffraction beam having a predetermined diffraction coefficient incident from the optical means 200 is focused. As shown in FIG. 310 ', the second photodetector 320', and the third photodetector 330 '.

Here, the first photodetector 310 'is divided into four regions (A), (B), (C) and (D) in which a central beam having a zero-order diffraction coefficient is focused among the diffraction beams.

In addition, the second photodetector 320 'is formed in the upper direction of the first photodetector 310', and side beams having a + 1st order diffraction coefficient are focused (E _A1 ) (E _B1 ), (E It is divided into eight areas of _A2 ) (E _B2 ), (F _A2 ) (F _B2 ) and (F _A1 ) (F _B1 ).

Here, in the (E _A2 ), (E _B2 ), and (F _A2 ), (F _B2 ) photodetection regions formed at the central portion of the second photodetector 320 ′, the tracking error signal is not imaged or the tracking error signal. Wherein the light intensity distribution of the light detection region is less than the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the diffraction beam is not focused at the track center. It is used to compensate for the tracking error offset caused by the.

Further, the third photodetector 330 'is formed in the lower direction of the first photodetector 310', and the side beams having the -first-order diffraction coefficient are focused (I _A1 ) (I _B1 ), (I _A2 ) (I _B2 ), (J _A2 ) (J _B2 ), and (J _A1 ) (J _B1 ) are divided into eight areas.

Here, the (I _A2 ), (I _B2 ) and (J _A2 ) (J _B2 ) photodetection regions formed in the central portion of the third photodetector 330 ′ do not have a tracking error signal or a tracking error signal. Wherein the light intensity distribution of the light detection region is less than the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the diffraction beam is not focused at the track center. It is used to compensate for the tracking error offset caused by the.

At this time, an optical spot formed by the center beam and the side beam of the diffraction beam coinciding with the track center of the DVD-RAM optical disc 400 having a track pitch of 1.23 μm as shown in FIG. 10 through the optical means 200. When 500 is focused on the first, second and third photodetectors 310 ', 320', 330 ', respectively, the photodetector 300 has a predetermined shape as shown in FIG. Differential Astigmatic Detection (DAD) using optical intensity distribution of the center beam and the side beam of the diffracted beam focused on the photodetectors 310 ', 320', 330 'divided into The focus error signal of the DVD-RAM optical disc 400 is detected.

(Equation 6)

Focus error signal (FES) = (A + C)-(B + D) + β ((E _A1 + E _A2 + F _B1 + F _B2 + I _A1 + I _A2 + J _B1 + J _B2 )

-(F _A1 + F _A2 + E _B1 + E _B2 + J _A1 + J _A2 + I _B1 + I _B2 )]

In addition, the light detecting means 300 is a differential push-pull method (DPP: Differential Push-) using the light intensity distribution of the center beam and the side beam of the diffracted beam focused on the light detectors 310 ', 320', 330 '. Pull) to detect a tracking error signal of the DVD-RAM optical disc 400.

(Equation 7)

Tracking error signal (TES) = (A + B)-(D + C)-β ((E _A1 + E _A2 + E _B1 + E _B2 + I _A1 + I _A2 + I _B1 + I _B2 )

-(F _A1 + F _A2 + F _B1 + F _B2 + J _A1 + J _A2 + J _B1 + J _B2 )】

At this time, when the optical disc 400 is a DVD ± R / RW optical disc having a narrower track pitch than a DVD-RAM optical disc, more specifically, a track pitch of 0.74 占 퐉 and a side beam does not coincide with the track center, optical detection is performed. The means 300 receives the focus error signal of the DVD ± R / RW optical disc 400 by astigmatism using the light intensity distribution of the first light detector 310 ′ where the center of gravity having a zeroth order diffraction coefficient is focused. Detect.

(Equation 8)

Focus error signal (FES) = (A + C)-(B + D)

In addition, the photodetecting means 300 is an intermediate region in which a tracking error signal is not formed in the second and third photodetectors 320 'and 330' in which side beams having a first-order diffraction coefficient are focused, more specifically. (E _A2 ) (E _B2 ), For compensating for the tracking offset that occurs when the light intensity distribution in the (F _A2 ) (F _B2 ), (I _A2 ) (I _B2 ), and (J _A2 ) (J _B2 ) areas is off the optical axis of the objective lens 250 The tracking error signal of the DVD ± R / RW optical disc 400 is detected by a modified push-pull (MPP) method used as the light intensity distribution.

(Equation 9)

Tracking error signal (TES) = (A + B)-(C + D)-β ((E _A2 + E _B2 + I _A2 + I _B2 )

-(F _A2 + F _B2 + J _A2 + J _B2 )]

(Third embodiment)

The light detecting means 300 is a place where the light spot 500 formed by the diffraction beam having a predetermined diffraction coefficient incident from the optical means 200 is focused. As shown in FIG. 310 ", the 2nd photodetector 320", and the 3rd photodetector 330 ".

Here, the first photodetector 310 ″ includes (A1) (B1), (A2) (B2), (D2) (C2), and (D1) (C1) in which a central beam having a zero-order diffraction coefficient is focused. It is divided into eight areas.

Here, the (A2) (B2) and (D2) (C2) photodetection regions formed in the central portion of the first photodetector 310 "are less likely to have a tracking error signal or are less affected by the tracking error signal. The light intensity distribution of the light detection region, wherein the light intensity distribution of the light detection region compensates for a tracking error offset caused by the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the side beams is not focused at the track center. Used to.

Further, the second photodetector 320 " is formed in the upper direction of the first photodetector 310 ", and the side beam having a + 1st order diffraction coefficient is focused (E _A1 ) (E _B1 ), (E It is divided into eight areas of _A2 ) (E _B2 ), (F _A2 ) (F _B2 ) and (F _A1 ) (F _B1 ).

Here, (E _A2 ) (E _B2 ) and (F _A2 ) (F _B2 ) photodetection in which the tracking error signal formed in the center region of the second photodetector 320 ″ is not imaged or is less affected by the tracking error signal. The light intensity distribution of the region is used to compensate for the tracking error offset caused by the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the side beams is not focused at the track center.

In addition, the third photodetector 330 ″ is formed in the lower direction of the first photodetector 310 ″, and the side beams having a -first-order diffraction coefficient are focused (I _A1 ) (I _B1 ), (I _A2 ) (I _B2 ), (J _A2 ) (J _B2 ), and (J _A1 ) (J _B1 ) are divided into eight areas.

Here, (I _A2 ) (I _B2 ) and (J _A2 ) (J _B2 ) photodetection in which the tracking error signal formed in the center region of the third photodetector 330 ″ is not imaged or is less affected by the tracking error signal. The light intensity distribution of the region is used to compensate for the tracking error offset caused by the optical side deviation of the objective lens with respect to the optical disk having a track pitch in which at least one side beam of the side beams is not focused at the track center.

At this time, the first, second and third light spots 500 formed by the center beam and the side beam of the diffraction beam coincident with the track center of the DVD-RAM optical disc having a track pitch of 1.23 mu m through the optical means 200 are provided. When focused on the photodetectors 310 ", 320", and 330 ", the photodetector 300 is diffracted to focus on the photodetectors 310", 320 ", and 330". The focus error signal of the DVD-RAM optical disc 400 is detected by differential astigmatic detection (DAD) using the light intensity distribution of the beam.

(Equation 10)

Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2)

+ β ((E _A1 + E _A2 + F _B1 + F _B2 + I _A1 + I _A2 + J _B1 + J _B2 )

-(F _A1 + F _A2 + E _B1 + E _B2 + J _A1 + J _A2 + I _B1 + I _B2 )]

In addition, the light detecting means 300 detects a tracking error signal of the DVD-RAM optical disc 400 by differential push-pull method (DAD: Differential Phase Detection) using the light intensity distribution of the center beam and the side beam focused on the light detecting unit. Detect.

(Equation 11)

Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)

β ((E _A1 + E _A2 + E _B1 + E _B2 + I _A1 + I _A2 + I _B1 + I _B2 )

-(F _A1 + F _A2 + F _B1 + F _B2 + J _A1 + J _A2 + J _B1 + J _B2 )】

At this time, when the optical disc 400 is a DVD ± R / RW optical disc in which a narrower track pitch, more specifically, a track pitch of 0.74 탆 is formed than a DVD-RAM optical disk and a side beam does not coincide with the track center, is detected. The means 300 detects the focus error signal of the DVD ± R / RW optical disc by astigmatism using the light intensity distribution of the first light detector 310 ″ in which the central beam having the zeroth order diffraction coefficient is focused. do.

(Equation 12)

Focus error signal (FES) = (A1 + C1)-(B1 + D1)

or,

Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2)

In addition, the light detecting means 300 includes light formed in the center region in which the tracking error signal is not formed among the second and third light detectors 320 "and 330" to which side beams having a first-order diffraction coefficient are focused. DVD ± R / RW optical disc 400 by the Modified Push-Pull (MPP) method, which uses the light intensity distribution of the detection area to compensate for tracking offsets caused by the deviation of the optical axis of the objective lens 250. ) Detects a tracking error signal.

(Equation 13)

Tracking error signal (TES) = (A1 + B1)-(C1 + D1)

β ((E _A2 + E _B2 + I _A2 + I _B2 )-(F _A2 + F _B2 + J _A2 + J _B2 )]

In addition, the photodetecting means 300 includes a photodetection region formed in the center region of the first, second and third photodetectors 310 ", 320 ", and 330 " where the tracking error signal is not formed. Tracking error of DVD ± R / RW optical disc by another modified push-pull (MPP) method, which uses the light intensity distribution as a compensation for the tracking offset caused by the deviation of the optical axis of objective lens 250 The signal can also be detected.

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(Equation 14)

Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)

β ((E _A2 + E _B2 + I _A2 + I _B2 )-(F _A2 + F _B2 + J _A2 + J _B2 )]

 Here, the detection of the focus / tracking error signal of the optical disc described in the above embodiment is characterized in that the center beam and the side beam of the diffraction beam coincide with the track center of the DVD-RAM optical disc and not with the track center of the DVD ± R / RW optical disc. Although described based on the state, it should be noted that the present invention is not limited thereto and may be applied to the reverse.

As described above, the present invention utilizes a light distribution focused on a photodetection area in which a tracking error signal is not formed among the photodetectors in which the center beam and side beams of the diffracted beams incident from an optical disk having a different track pitch are focused. Compensate for the tracking offset caused by the deviation of the optical axis of the objective lens.

Therefore, the present invention simultaneously performs tracking / focus servo tracking for optical discs having different track pitches by compensating tracking offsets due to deviations in the optical axis of the objective lens using the optical distribution of the photodetection area where the tracking error signal is not formed. It provides the effect that you can.

Herein, the present invention described above has been described with reference to preferred embodiments, but those skilled in the art will variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. And can be changed.

Claims (22)

Light emitting means for emitting a single beam focused on a track of an optical disc having a different track pitch to the outside; Optical means for concentrating a light spot of a diffraction beam having a predetermined diffraction coefficient formed by performing diffraction on the single beam to the track, and transmitting the diffraction beam reflected by the track to the outside; And A first light detector configured to focus a center beam having a zeroth order diffraction coefficient among second diffraction beams incident from the optical means, and second and third light detectors focused on a side beam having a first order diffraction coefficient, respectively, The photodetector is divided into a predetermined number of photodetection regions, and at least one photodetector is formed with a photodetection region in which a tracking error signal used for compensating for a tracking error offset caused by the deviation of the optical axis of the objective lens is not formed. Photodetector Optical pickup device, characterized in that configured to include. The method of claim 1, When the center beam and the side beam of the diffraction beam coincide with the track center of the optical disk, the focus error signal is detected by differential astigmatism using the light distribution of the first light detector in which the center beam having the zeroth order diffraction coefficient is focused. The tracking error signal is detected by a differential push-pull method using a light distribution focused on each of the photodetectors. If at least one side beam of the diffraction beams does not coincide with the track center of the optical disc, the focus error signal is detected by astigmatism using the light distribution of the first light detector in which the center beam having the zeroth order diffraction coefficient is focused. And a tracking error signal is detected by a modified push-pull method using a light distribution of the photodetector in which a photodetection region in which a tracking error signal is not formed is used for tracking error offset compensation. The method of claim 1, wherein the optical means, A diffraction plate which diffracts the beam emitted from the light emitting means to form a diffraction beam having a linear polarization shape having a predetermined diffraction coefficient; A beam splitter for branching a linearly polarized diffraction beam incident from the diffraction plate in a direction of an optical disk, and for branching a linearly diffracted diffraction beam reflected from the optical disk to the light detecting means; A collimator lens for converting a diffracted beam in the form of linearly flat light incident from the beam splitter into parallel light; The wavelength plate which transforms parallel light incident through the collimator lens into a circularly polarized diffraction beam, converts the circularly-shaped diffraction beam reflected from the optical disk into a linearly-flat diffraction beam, and emits it to the collimator lens. ; And An objective lens for converging a circularly polarized diffraction beam incident from the wave plate to form a light spot having a predetermined shape at a track pitch of the optical disc Optical pickup device comprising a. The method of claim 1, The first photodetector is divided into eight (A1) (B1), (A2) (B2), (D2) (C2), and (D1) (C1) photodetection areas in which a central beam having a zero-order diffraction coefficient is focused. The tracking error signal is not imaged in (A2) (B2) and (D2) (C2) which are the light detection areas of the center area among the light detection areas. The second photodetector is formed in an upper direction of the first photodetection region, and is divided into four (E1) (E2) and (F1) (F2) photodetection regions in which side beams having a + 1st order diffraction coefficient are focused. , The third photodetector is formed in the lower direction of the first photodetection region, and is divided into four (I1) (I2) and (J1) (J2) photodetection regions in which side beams having a -first-order diffraction coefficient are focused. Optical pickup device, characterized in that. The method of claim 4, wherein the light detecting means, When the center beam and the side beam of the diffraction beam coincide with the track center of the optical disk, differential astigmatic detection (DAD) is performed according to the light intensity distribution of the center beam and the side beam focused on the light detector, respectively. Next relation used Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2)                         + β ((E1 + F2 + I1 + J2)-(F1 + F2 + J1 + I2)] And a focus error signal is detected using the optical pickup device. The method of claim 4, wherein the light detecting means, When the center beam and the side beam of the diffraction beam coincide with the track center of the optical disk, the differential push-pull method (DPP) is performed by the light intensity distribution of the center beam and the side beam that are focused on the light detector, respectively. Next relation used Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)                         β ((E1 + E2 + I1 + I2)-(F1 + F2 + J1 + J2)] And a tracking error signal is detected using the optical pickup device. The method of claim 4, wherein the light detecting means, When at least one side beam of the diffraction beams does not coincide with the track center of the optical disk, astigmatism by the light intensity distribution of the first light detector in which a center beam having a zero-order diffraction coefficient is focused is then used. Relation Focus error signal (FES) = (A1 + C1)-(B1 + D1) And a focus error signal is detected using the optical pickup device. The method of claim 4, wherein the light detecting means, If at least one side beam of the diffraction beams does not coincide with the track center of the optical disc, another astigmatism is caused by the light intensity distribution of the first light detector in which the center beam having the zeroth order diffraction coefficient is focused. Next relation used Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2) And a focus error signal is detected using the optical pickup device. The method of claim 4, wherein the light detecting means, If at least one of the side beams of the diffraction beams does not coincide with the track center of the optical disc, a modified push that uses the light intensity distribution of the center area where the tracking error signal of the first light detector is not formed for tracking error offset compensation -Pull method (MPP: Modified Push-Pull) Tracking error signal (TES) = (A1 + B1)-(C1 + D1)-β ((A2 + B2)-(C2 + D2)] And a tracking error signal is detected using the optical pickup device. The method of claim 4, wherein the light detecting means, If at least one side beam of the diffraction beams does not coincide with the track center of the optical disc, another light intensity distribution of the center area where the tracking error signal of the first light detector is not formed is used for tracking error offset compensation. The following relation using Modified Push-Pull (MPP) Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2)                         β ((A2 + B2)-(C2 + D2)) And a tracking error signal is detected using the optical pickup device. The method of claim 1, The first photodetector is divided into four (A) (B) and (D) (C) photodetection regions in which a central beam having a zeroth order diffraction coefficient is focused, The second photodetector is formed in an upper direction of the first photodetector to focus side beams having a + 1st order diffraction coefficient (E _A1 ), (E _B1 ), (E _A2 ) (E _B2 ), and (F _A2 ) (F _B2 ) and (F _A1 ) (F _B1 ) are divided into eight photodetection areas, and among the photodetection areas, the photodetection areas E _A2 (E _B2 ) and (F _A2 ) (F _B2 ) The tracking error signal is not missing, The third photodetector is formed in a lower direction of the first photodetector such that side beams having a first order diffraction coefficient are focused on (I _A1 ), (I _B1 ), (I _A2 ) (I _B2 ), and (J _A2 ) It is divided into (J _B2 ), (J _A1 ) (J _B1 ) photodetection areas, and the photodetection areas (I _A2 ) (I _B2 ) and (J _A2 ) (J _B2 ) of the center area among the photodetection areas. An optical pickup apparatus, wherein the tracking error signal is not lost. The method of claim 11, wherein the light detecting means, When the center beam and the side beam of the diffraction beam coincide with the track center of the optical disk, a differential astigmatic method (DAD: Differential Astigmatic Detection) based on the light intensity distribution of the center beam and the side beam focused on the light detection unit, respectively, is used. Next relation Focus error signal (FES) = (A + C)-(B + D) + β ((E _A1 + E _A2 + F _B1 + F _B2 + I _A1 + I _A2 + J _B1 + J _B2 ) -(F _A1 + F _A2 + E _B1 + E _B2 + J _A1 + J _A2 + I _B1 + I _B2 )] And a focus error signal is detected using the optical pickup device. The method of claim 11, wherein the light detecting means, When the center beam and the side beam of the diffraction beam coincide with the track center of the optical disk, the differential push-pull method (DPP) is performed by the light intensity distribution of the center beam and the side beam that are focused on the light detector, respectively. Next relation used Tracking error signal (TES) = (A + B)-(C + D)-β ((E _A1 + E _A2 + E _B1 + E _B2 + I _A1 + I _A2 + I _B1 + I _B2 ) -(F _A1 + F _A2 + F _B1 + F _B2 + J _A1 + J _A2 + J _B1 + J _B2 )】 And a tracking error signal is detected using the optical pickup device. The method of claim 11, wherein the light detecting means, When at least one side beam of the diffraction beams does not coincide with the track center of the optical disk, astigmatism is generated by the light intensity distribution of the first light detector in which a center beam having a zeroth order diffraction coefficient is focused. Relation Focus error signal (FES) = (A + C)-(B + D) And a focus error signal is detected using the optical pickup device. The method of claim 11, wherein the light detecting means, When the at least one side beam of the diffraction beams does not coincide with the track center of the optical disk, the light intensity distribution of the center area where the tracking error signal is not formed in the second and third light detectors is used for tracking error offset compensation. The following relation using Modified Push-Pull (MPP) Tracking error signal (TES) = (A + B)-(C + D)-β ((E _A2 + E _B2 + I _A2 + I _B2 ) -(F _A2 + F _B2 + J _A2 + J _B2 )] And a tracking error signal is detected using the optical pickup device. The method of claim 1, The first photodetector is divided into eight (A1) (B1), (A2) (B2), (D2) (C2), and (D1) (C1) photodetection areas in which a central beam having a zero-order diffraction coefficient is focused. The tracking error signal is not imaged in the photodetection areas A2, B2 and D2 and C2 of the center area among the photodetection areas. The second photodetector is formed in an upper direction of the first photodetector, and side beams having a first order diffraction coefficient are focused on (E _A1 ), (E _B1 ), (E _A2 ) (E _B2 ), and (F _A2) (F _B2 ), (F _A1 ) (F _B1 ) divided into eight photodetection areas, and the photodetection areas E _A2 (E _B2 ) and (F _A2 ) (F _B2 ) of the central area among the photodetection areas. Tracking error signal is not lost The third photodetector is formed in a lower direction of the first photodetector, and side beams having a -first-order diffraction coefficient are focused on (I _A1 ) (I _B1 ), (I _A2 ) (I _B2 ), and (J _A2) (J _B2 ), (J _A1 ) (J _B1 ) divided into 8 light detection areas, and the light detection areas I _A2 (I _B2 ) and (J _A2 ) (J _B2 ) of the center area among the light detection areas. And a tracking error signal is not formed in the optical pickup device. The method of claim 16, wherein the light detecting means, When the center beam and the side beam of the diffraction beams coincide with the track centers of the optical disk, a differential astigmatic method (DAD: Differential Astigmatic Detection) based on the light intensity distribution of the center beam and the side beams focused on the light detection units, respectively, Next relation Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2) + β ((E _A1 + E _A2 + F _B1 + F _B2 + I _A1 + I _A2 + J _B1 + J _B2 ) -(F _A1 + F _A2 + E _B1 + E _B2 + J _A1 + J _A2 + I _B1 + I _B2 )] And a focus error signal is detected using the optical pickup device. The method of claim 16, wherein the light detecting means, When the center beam and the side beam of the diffraction beams coincide with the track center of the optical disk, the differential push-pull method (DPP: Differential Push-Pull) by the light intensity distribution of the center beam and the side beam that are focused on the light detector, respectively Next relation using Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2) β ((E _A1 + E _A2 + E _B1 + E _B2 + I _A1 + I _A2 + I _B1 + I _B2 ) -(F _A1 + F _A2 + F _B1 + F _B2 + J _A1 + J _A2 + J _B1 + J _B2 )】 And a tracking error signal is detected using the optical pickup device. The method of claim 16, wherein the light detecting means, If at least one of the side beams of the diffraction beams does not coincide with the track center of the optical disk, astigmatism by the light intensity distribution of the first light detector in which the center beam having the zeroth order diffraction coefficient is focused is then used. Relation Focus error signal (FES) = (A1 + C1)-(B1 + D1) And a focus error signal is detected using the optical pickup device. The method of claim 16, wherein the light detecting means, If at least one side beam of the diffraction beams does not coincide with the track center of the optical disc, another astigmatism is caused by the light intensity distribution of the first light detector in which the center beam having the zeroth order diffraction coefficient is focused. Next relation used Focus error signal (FES) = (A1 + A2 + C1 + C2)-(B1 + B2 + D1 + D2) And a focus error signal is detected using the optical pickup device. The method of claim 16, wherein the light detecting means, When the at least one side beam of the diffraction beams does not coincide with the track center of the optical disk, the light intensity distribution of the center area where the tracking error signal is not formed in the second and third light detectors is used for tracking error offset compensation. The following relation using Modified Push-Pull (MPP) Tracking error signal (TES) = (A1 + B1)-(C1 + D1) β ((E _A2 + E _B2 + I _A2 + I _B2 )-(F _A2 + F _B2 + J _A2 + J _B2 )] And a tracking error signal is detected using the optical pickup device. The method of claim 16, wherein the light detecting means, If at least one side beam of the diffraction beams does not coincide with the track center of the optical disc, tracking error offset compensation is performed for the light intensity distribution in the center region where the tracking error signals of the first, second and third light detectors are not formed. The following relation using Modified Push-Pull (MPP) Tracking error signal (TES) = (A1 + A2 + B1 + B2)-(C1 + C2 + D1 + D2) β ((E _A2 + E _B2 + I _A2 + I _B2 )-(F _A2 + F _B2 + J _A2 + J _B2 )] And a tracking error signal is detected using the optical pickup device.

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